This invention relates to spraying apparatus. It is particularly but not exclusively concerned with crop spraying, either with fertilizers, minerals, or with various killing agents, such as pesticides, insecticides, herbicides, and fungicides. These may be in liquid, dust or granule form. Seeds may be sown by such a system.
Tow mechanised crop spraying systems are generally known. One employs aircraft, the other a ground based vehicle such as a tractor. Fixed wing aircraft have to make `runs` over the spraying area, which requires extreme accuracy of positioning and hazardous low level flying. There is a limit to the minimum height that can be safely flown, and there is a tendency for the sprayed medium to drift, causing double coverage of some spraying swathes, inadequate coverage or `holidays` in others, or spraying of unwanted gases. This is wasteful and can be dangerous. Helicopters are more expensive to operate, their downdraught may interfere with the spray and can adamage fragible crops, and they have some of the drawbacks of fixed wing aircraft. In both cases the payload is limited and replenishment wasteful in time and fuel. All aerial spraying is governed much more rigorously by suitable weather conditions than is spraying from the ground.
The other common crop spraying system employs a tractor carrying or towing a tank of the spraying medium and fitted with a transverse boom (or a boom each side) with spray nozzles. This can only be of limited span, it tends to `whip` on any but the smoothest ground, giving uneven spraying, and the manoeuvrability of the tractor in the corners of a field is restricted, often resulting in uneven treatment. Also, the tractor has to make a considerable number of passes to cover a given area, resulting in crop damage, reduced yield and soil compaction.